I have heard many times from patients who suffered from joint pain that they were warned by well-wishing friends and family to avoid taking soybeans and soy products. There is a common belief that soy can cause inflammation and exacerbate the pain. In fact, this is a myth.

Soy isoflavones and inflammation

Soy and soy food are rich in a group of flavonoids called isoflavones. Research has shown that isoflavones, including daidzein and genistein, possess antioxidant, anticancer, antimicrobial, and anti-inflammatory activities [1]. Perhaps one of the most renown properties of isoflavones is the ability to act as a weak estrogen that can bind to the estrogen receptor and block the binding of the more potent endogenous estrogens, potentially play a role in the prevention of hormone-related cancer like breast cancer, cervical cancer, and the male prostate or testicular cancer [1].

The anti-inflammatory effects of isoflavones stern from the ability to down-regulate the pro-inflammatory cytokines, the small signalling proteins that can trigger the cascading response of inflammation in the body [2]. Pro-inflammatory cytokines, such as Tumor Necrosis Factor-α (TNF-α), also play an important role in the process of pain in the body.  In one clinical trial, postmenopausal women taking soymilk containing isoflavones daily for 16 weeks were found to have a 25% lower TNF-α level at the end of the study compared to their initial level [3]. In another study, men with prostate cancers who took 2 slices of soy bread daily also shown to have decreased levels of many types of pro-inflammatory cytokines after 56 days [4]. Hence, soy is good for reducing inflammation and pain, not the contrary.

Soy and osteoarthritis

One of the most common causes of joint pain is arthritis, either osteoarthritis or rheumatoid arthritis. Osteoarthritis is the result of the loss of joint cartilage. In a double-blind placebo-control clinical trial, 154 patients with osteoarthritis were randomly assigned to receive either a soy-protein supplement or a milk-based protein supplement daily for 3 months. The results showed that soy-protein supplement improved symptoms of osteoarthritis including pain and range of motion as well as the quality of life. Blood tests also showed that there was an improvement in cartilage synthesis and reduction of cartilage degradation [5].

Combining avocado and soybean as a dietary supplement (ASU) has also been shown to be a potential treatment option for osteoarthritis as it was shown to reduce the progression of joint-space loss in osteoarthritis [6]. A 6-month observational study with 4822 osteoarthritis patients treated with ASU also found the supplement to be able to alleviate joint pain, improve functional ability and achieve a significant reduction in painkillers intake among the patients [7]. In another study that used X-ray to examine the knee joints of 5764 men and women, soy milk intake was found to significantly associate with fewer osteophytes, i.e. bone spurs, that may cause knee pain [8].

Soy and rheumatoid arthritis

As for rheumatoid arthritis, the anti-inflammatory effects of isoflavones have also been studied in an animal model, showing promising results in improving symptoms, prevention of tissue damage, and reduction in joint inflammation [9]. Hydrolyzed soy protein was used in an elemental diet to treat rheumatoid arthritis in one human study. Patients who took the special diet had less pain and better joint function for the duration of the study compared to those who were on normal diet [10]. Particularly, black soybean has been recommended as an anti-inflammatory food for rheumatoid arthritis due to the rich content of anthocyanin [10], a plant antioxidant that has been shown to have anti-arthritic effects [11].

Soy and gout

Another potential cause of joint pain is gout. This is due to the build-up of uric acid in the joint. The crystallization of excess uric acid can lead to inflammation and pain. Soybeans all legumes have been blamed for its content of purine that can exacerbate the build-up of uric acid. I have written on this topic previously in an earlier blog post (See “Don’t Keep Bean Out of your Diet”). The fact is purine-rich vegetables or protein is not associated with an increased risk of gout!

Data from the Singapore Chinese Health Study provided the best evidence. In an analysis of the data to examine the relationship between the consumption of dietary protein from each of its major sources and the risk of gout in a Chinese population, researchers found dietary intake of soy and non-soy legumes was associated with a reduced risk of gout contrasting the higher total dietary protein intake from mainly poultry and fish/shellfish was associated with an increased risk of gout [12]. Such findings echo my advice in the previous blog post, and I repeat: “for meat eaters, if you are scared of gout, please cut down your meat and fish consumption first before finding culprits in beans and lentils”.

Health benefits of soy

Nutritionally, soybean is a source of high-quality protein and healthful fat. It is low in carbohydrates, rich in calcium, potassium, iron, zinc, as well as vitamin B2, B3, B6, and K [13]. Regular consumption of soy food has been associated with many health benefits including reduce risk of cardiovascular disease (by lowering bad cholesterol and blood pressure, improve blood circulation, and reduce inflammation), improve bone health, lower risk of breast cancer, preserve kidney function, ameliorate menopausal symptoms, and enhance cognitive function as well as mental resilience [13]. Hence, soy food is undoubtedly a good addition to any diet. It is recommended to replace less healthy foods (e.g. high-fat animal-based food) with soy and as part of an overall healthy diet to lower the risk of chronic disease [13].

Conclusion

The fear that soy food may exacerbate joint pain is completely unfounded. Soy contains isoflavones which are excellent anti-inflammatory agents that can help to reduce pain and improve functionality in all major causes of joint pain: osteoarthritis, rheumatoid arthritis, and gout. With so many health benefits associated with increased soy consumption, there is no reason to avoid soy food unless one is allergic to it, which is very rare.

References

[1]        J. Yu, X. Bi, B. Yu, D. Chen, Isoflavones: Anti-Inflammatory Benefit and Possible Caveats, Nutrients. 8 (2016) 361. doi:10.3390/nu8060361.

[2]        W.E. Hardman, Diet components can suppress inflammation and reduce cancer risk., Nutr. Res. Pract. 8 (2014) 233–40. doi:10.4162/nrp.2014.8.3.233.

[3]        Y. Huang, S. Cao, M. Nagamani, K.E. Anderson, J.J. Grady, L.-J.W. Lu, Decreased Circulating Levels of Tumor Necrosis Factor-α in Postmenopausal Women during Consumption of Soy-Containing Isoflavones, J. Clin. Endocrinol. Metab. 90 (2005) 3956–3962. doi:10.1210/jc.2005-0161.

[4]        G.B. Lesinski, P.K. Reville, T.A. Mace, G.S. Young, J. Ahn-Jarvis, J. Thomas-Ahner, Y. Vodovotz, Z. Ameen, E. Grainger, K. Riedl, S. Schwartz, S.K. Clinton, Consumption of soy isoflavone enriched bread in men with prostate cancer is associated with reduced proinflammatory cytokines and immunosuppressive cells., Cancer Prev. Res. (Phila). 8 (2015) 1036–44. doi:10.1158/1940-6207.CAPR-14-0464.

[5]        B.H. Arjmandi, D.A. Khalil, E.A. Lucas, B.J. Smith, N. Sinichi, S.B. Hodges, S. Juma, M.E. Munson, M.E. Payton, R.D. Tivis, A. Svanborg, Soy protein may alleviate osteoarthritis symptoms, Phytomedicine. 11 (2004) 567–575. doi:10.1016/j.phymed.2003.11.001.

[6]        B.A. Christiansen, S. Bhatti, R. Goudarzi, S. Emami, Management of Osteoarthritis with Avocado/Soybean Unsaponifiables., Cartilage. 6 (2015) 30–44. doi:10.1177/1947603514554992.

[7]        P. Głuszko, M. Stasiek, Symptom-modifying effects of oral avocado/soybean unsaponifiables in routine treatment of knee osteoarthritis in Poland. An open, prospective observational study of patients adherent to a 6-month treatment., Reumatologia. 54 (2016) 217–226. doi:10.5114/reum.2016.63661.

[8]        H. Li, C. Zeng, J. Wei, T. Yang, S. Gao, Y. Li, W. Luo, W. Xiao, Y. Xiong, G. Lei, Relationship between soy milk intake and radiographic knee joint space narrowing and osteophytes, Rheumatol. Int. 36 (2016) 1215–1222. doi:10.1007/s00296-016-3491-6.

[9]        M. Mohammad-Shahi, F. Haidari, B. Rashidi, A.A. Saei, S. Mahboob, M.-R. Rashidi, Comparison of the effects of genistein and daidzein with dexamethasone and soy protein on rheumatoid arthritis in rats., Bioimpacts. 1 (2011) 161–70. doi:10.5681/bi.2011.022.

[10]      S.E. Holst-Jensen, M. Pfeiffer-Jensen, M. Monsrud, U. Tarp, A. Buus, I. Hessov, E. Thorling, K. Stengaard-Pedersen, Treatment of rheumatoid arthritis with a peptide diet: a randomized, controlled trial., Scand. J. Rheumatol. 27 (1998) 329–36. http://www.ncbi.nlm.nih.gov/pubmed/9808394 (accessed November 12, 2018).

[11]      H.K. Min, S.-M. Kim, S.-Y. Baek, J.-W. Woo, J.-S. Park, M.-L. Cho, J. Lee, S.-K. Kwok, S.W. Kim, S.-H. Park, Anthocyanin Extracted from Black Soybean Seed Coats Prevents Autoimmune Arthritis by Suppressing the Development of Th17 Cells and Synthesis of Proinflammatory Cytokines by Such Cells, via Inhibition of NF-κB, PLoS One. 10 (2015) e0138201. doi:10.1371/journal.pone.0138201.

[12]      G.G. Teng, A. Pan, J.-M. Yuan, W.-P. Koh, Food Sources of Protein and Risk of Incident Gout in the Singapore Chinese Health Study, Arthritis Rheumatol. 67 (2015) 1933–1942. doi:10.1002/art.39115.

[13]      M. Messina, Soy and Health Update: Evaluation of the Clinical and Epidemiologic Literature., Nutrients. 8 (2016). doi:10.3390/nu8120754.